Detecting entanglement of quantum channels

Chaojian Li,Bang-Hai Wang,Bujiao Wu,Xiao Yuan

Figure 3. (a) An example quantum circuit consisting of two CZ gates with local depolarizing noise. The Choi state of (a) is equivalent to (b) the graph state $\left|{G}_{\mathrm{CZ}}\right\rangle $ up to local unitary rotation.